<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
.demo1{
    height:100px;
    width:100px;
    background:gold;
    border-radius: 12px;
    position: relative;
    margin: 50px auto 0;
}
.demo1 div{
    width: 28px;
    height: 28px;
    background: red;
    line-height: 28px;
    text-align: center;
    position: absolute;
    right: -14px;
    top: -14px;
    border-radius: 50%;
}
.demo2{
    height: 100px;
    background: red;
}
 img,span{
margin-top: 1500px;   
}
.demo3{
    width: 500px;
    height: 300px;
    background: green;
    position: fixed;
    top:50%;
    left: 50%;
    margin-left: -250px;
    margin-top: -150px;
    z-index: 100;
}
.demo3 h3{
    background-color: yellow;
}
.demo4{
    width: 100%;
    height: 100%;
    background-color: black;
    position: fixed;
    top: 0;
    left: 0;
    opacity: 0.5;
}
    </style>
</head>
<body>
    <div class="demo1">
        <div>5</div>
    </div>
    <hr>
    <div class="demo2">菜单标题</div>
    <div>
        <div class="demo3">
            <h3>标题</h3>
        </div>
        <div class="demo4"></div>
    </div>
  <img src="./imgs/bg01.png" alt="图片加载失败">
  <span>qdasfasferfasdf</span>
  <img src="./imgs/hnkz.jpg" alt="图片加载失败">
    </div>
</body>
</html>